The invention concerns a process and apparatus for the purification of contaminated sulfur.
To remove the sulfur obtained from the refining of petroleum and natural gas in large volumes and stored in large numbers of blocks, it is known (see U.S. Pat. Nos. 4,171,200 and 4,203,625), either (a) to drill holes in the blocks of sulfur and insert heating tubes through which steam is conducted in order to melt off parts of the blocks, or (b) to transform the solid sulfur into the liquid state by means of mobile devices with heating means mounted on them, then remove the sulfur through pipes and reconvert it later into the solid state. These thermal removal processes are used, because removal by mechanical means such as excavators, is not permissible in view of the dust generated in the process.
It is further known in regard to thermal sulfur removal processes (see Hamilton Tubular Sulphur Melter, published by Canadian Pump and Paper Association, Montreal, Meeting of Jan. 24-26, 1946), to transfer the melting heat by direct contact of the raw sulfur with heated surfaces, or to use already molten sulfur as the heat transfer medium. After a certain initial phase, the molten sulfur melts and is collected to flat pans.
It has also been attempted in a similar manner (see Alberta Sulfur Symposium, "Proceedings of Sulfur 84" Sulphur Development of Canada, pgs. 418-420), to purify contaminated sulfur by collecting small broken pieces of sulfur in a vessel with a funnel-shaped bottom. The vessel is equipped with heating devices which are in contact with the sulfur pieces. The melting sulfur is to flow downward and be obtained in the purified state after passing through several coarse and fine filters arranged successively.
Installations of a similar type (see U.S. Pat. No. 2,149,373), comprise a steam-heated, cylindrical pipe for the melting of sulfur pieces, the pipe being placed vertically over a heated funnel and closed on the bottom with an adjustable cone. In the funnel, which has an overflow on top, the molten sulfur is purified. Fine residual impurities are removed at the bottom of the funnel. Installations of this type have the disadvantage that, in contrast to the melting of relatively pure sulfur, they become unusable after a relatively short period of time, because they become coated with sulfur. That is, at least a portion of the impurities separated from the sulphur is deposited on the heating devices or the cone and, depending upon the properties of the sulfur, the sulfur solidifies and bakes thereon. Furthermore, while the water content of the sulfur evaporates in the area of the heating devices, it is recondensed upon rising into the cooler zones of the melting vessel or the cylindrical pipe, so that the water must be evaporated several times.
It is known that sulfur conducts heat very poorly so that contaminated heating devices are no longer able to perform the melting process after a relatively short period of time. This is particularly true if the sulfur is to be removed from the area of the aforementioned storage blocks located in the vicinity of the ground surface or even below it. The proportion of contamination contained in the sulphur is too large to permit the undisturbed operation of such known purification installations for any length of time. It is, therefore, a disadvantage of these installations that they must be cleaned relatively often, during which cleaning operations, the installations must be shut down, so that a continuous purification of sulfur is not possible.
This disadvantage is not characteristic of another known apparatus for the recovery of sulfur from minerals (see German No. OS-20 14 613), in which water is heated in an autoclave under pressure to temperatures above the melting point of sulfur and used to heat the sulfur. The portion of the mineral not containing sulfur is removed by means of a rotating screen for the pressurized water and from the sulfur settling in the pressurized water due to difference in specific gravity. A disadvantage of that process involves the expense of manufacturing and operating the pressurized vessel and obtaining the sulfur from a refining cell provided therein.
It is, therefore, an object of the present invention to provide a process and apparatus of the afore-mentioned type so that even heavily contaminated sulfur may be purified with a high degree of efficiency without incurring excessive costs.